According to HP memristor model, a grounded memristor emulator is proposed in this paper. Based on the proposed memristor emulator, a universal emulator of mem-elements is implemented with common off-the-shelf components. This universal emulator can transform the grounded memristor into a floating memristor, or a floating meminductor, or a floating memcapacitor by connecting different components to it. Because the universal emulator is floating, it is not confined to be grounded and can be connected between any two voltages. In order to verify theoretical presumptions about the universal emulator, Pspice simulations are conducted on this circuit.